Alkaline cells, which may be operated either as cells or incorporated in batteries, and being either primary or secondary types, have been known for a considerable period of time. Such cells generally have zinc as the major anode component, usually in the form of a zinc amalgam powder or screen, but may have other anodes such as, for example, cadmium. Such cells may also have a variety of cathode depolarizers, such as silver oxide, mercuric oxide, manganese dioxide, nickel oxide, air, etc.; and may, as noted, be primary or secondary.
A common feature of such cells is that they have an alkaline electrolyte comprising an aqueous solution of an alkali metal or ammonium hydroxide such as sodium hydroxide, potassium hydroxide, lithium hydroxide, or the like. In any event, the cell is retained in a conductive container or can which has a positive terminal electrically associated with the cathode and a negative terminal electrically associated with the anode; the positive and negative terminals being electrically insulated from each other. The separator may comprise one or more than one layer, at least one of which is an electrolyte absorbent separator and another of which may be an ionically conductive barrier layer. The positive and negative terminals are electrically insulated one from the other by a grommet or insulating sleeve, and the cell is generally sealed or closed by crimping, tooling or swaging.
Various adjuvants may be included in such cells. For example, the anode mixture may have up to 10% by weight of mercury and up to 3% by weight of a gelling agent or thickening agent of the sort generally used for alkaline electrolytes, (for example carboxymethyl cellulose) together with zinc powder. Similarly, there may be up to 8% zinc oxide dissolved in the electrolyte. The separator may comprise a cellulosic or other electrolyte permeable polymer material. Depending on the size of the cell, and the nature of the system in which it is used, the anode may be placed in the cell in the form of a pellet or a gel, or poured into a cavity containing electrolyte.
The use of surfactants in cells has been known. For example, Ruetschi et al., in U.S. Pat. No. 3,057,944 issued Oct. 9, 1962, disclose a silver oxide cathode in a primary or secondary system having a surface active heteropolar substance admixed either to the electrolyte or to the silver oxide cathode.
Paterniti, in U.S. Pat. No. 3,847,669 issued Nov. 12, 1974, discloses the incorporation of an ethylene oxide polymer in a zinc/manganese dioxide cell so as to reduce the amount of mercury component required in a cell to provide adequate shelf life therefor. The ethylene oxide additives used by Paterniti are generally soluble in water, and may be used either to pre-wet the separator or they may be added directly to the zinc during the preparation of a gel from which the anode is formed.
Bauer et al., in U.S. Pat. No. 3,963,520, issued June 15, 1976 incorporate a corrosion inhibitor in the form of a saturated or unsaturated monocarboxylic acid with at least two ethanolamide radicals. Bauer et al. teach that their inhibitor may be dispersed in the zinc powder, or that it may be incorporated in the separator or added to the electrolyte. Bauer et al., together with Paterniti, have as their prime purpose to reduce the amount of mercury incorporated in the cell.
Lee, in U.S. Pat. No. 3,653,965 issued Apr. 4, 1972, discloses a rechargeable galvanic cell having a zinc anode and a zinc-containing electrolyte. Lee incorporates ethylene oxide polymers or their derivatives in the electrolyte, so as to suppress zinc dendrite formation during the charging cycle of the cell, thereby precluding or inhibiting the growth of zinc dendrites which can pierce the separator and ultimately cause internal short circuit within the cell.
Dirkse, in U.S. Pat. No. 3,348,973 issued Oct. 24, 1967, discloses a secondary battery where an additive having the general formula of tridecyloxypoly(ethylenoxy) ethanol is incorporated in the electrolyte or in the zinc anode, preferably in the zinc anode. Dirkse states that the life of the cell is significantly prolonged by use of the additive.